Barless closed loop color control

Abstract

A system and processes for the accurate measurement and control of image color values on a printing press with or without the presence of a color bar. More particularly, a barless color control system and processes for controlling the color quality of color images printed on a substrate online or offline, with or without a color bar printed on the substrate. The system provides an efficient and inexpensive method for barless closed loop color control and the processes are conducted without pixel-by-pixel comparisons.

1. A process for measuring and controlling a color value of one or more colored image portions which are printed on a planar substrate in a plurality of ink zones that extend across a width of the substrate, each colored image portion comprising one or more colors, wherein each color has a pure color value, the process comprising:
 (a) providing one or more colored image portions which are printed on a planar substrate with a quantity of ink in a plurality of ink zones that extend across a width of the substrate, each colored image portion comprising one or more colors, wherein each color has a pure color value; 
 (b) providing a memory which contains pure color value information in digital form for each color; 
 (c) providing a pixellated digital representation of said one or more colored image portions, said pixellated digital representation being divided into a plurality of digital paths corresponding to each of said ink zones, each digital path comprising a plurality of digital zones, and said pixellated digital representation being further divided into one or more color layers, each color layer corresponding to one of said one or more colors, and wherein said pixellated digital representation comprises target color values that correspond to the quantity of ink required to reproduce the one or more colored image portions for each color within each ink zone on the substrate; 
 (d) analyzing each of the color layers within each of the digital paths to determine a maximum pixel population area for each color within each of said digital paths, the maximum pixel population area having position coordinates and comprising a location within the colored image portion within the digital zone of a digital path having the target color value that is the closest target color value to the pure color value for its corresponding color within its digital path, and storing the maximum pixel population area position coordinates and its color value in the memory; 
 (e) comparing and determining any difference between the target color value of said maximum pixel population area and the corresponding pure color value for each color, and storing said difference in the memory; 
 (f) providing at least one imaging assembly, wherein the imaging assembly is capable of capturing digital representations of said one or more colored image portions; 
 (g) controlling the positioning and linear movement of said imaging assembly across the planar substrate; 
 (h) selecting and acquiring one or more digital images with the imaging assembly of said one or more colored image portions on the substrate at the maximum pixel population area location for at least one of said colors in at least one of said ink zones, thereby producing the digital image of the substrate at the maximum pixel population area; said digital image of the substrate at the maximum pixel population area having an actual color value for said at least one color in said at least one of said ink zones; 
 (i) analyzing the digital image of the substrate at the maximum pixel population area and measuring the actual color value for said at least one color; 
 (j) comparing and determining any difference between the actual color value and the pure color value, and storing said difference in the memory; and 
 (k) optionally adjusting the ink quantity on the substrate in the corresponding ink zone such that the difference between the actual color value and the pure color value is equivalent to the difference between said target color value and said pure color value determined in (e). 
 
     
     
       2. The process of  claim 1  option of adjusting the ink quantity on the substrate in step (k) is performed. 
     
     
       3. The process of  claim 1  further comprising repeating steps (g) through (k) to maintain color on the substrate such that the difference between the actual color value and the pure color value is equivalent to the difference between said target color value and said pure color value determined in (e) for each ink zone. 
     
     
       4. The process of  claim 1  wherein steps (g) through (k) are repeated for each color of said one or more colored image portions. 
     
     
       5. The process of  claim 1  wherein the target color values of said pixellated digital representation are obtained by scanning the substrate with a scanner. 
     
     
       6. The process of  claim 1  wherein the target color values of said pixellated digital representation are obtained by scanning the substrate with said imaging assembly. 
     
     
       7. The process of  claim 1  wherein said imaging assembly comprises a digital camera and at least one illumination source. 
     
     
       8. The process of  claim 7  wherein the illumination source either continuously or intermittently illuminates the one or more colored image portions. 
     
     
       9. The process of  claim 7  wherein the illumination source comprises a strobe comprising one or more white light emitting diodes. 
     
     
       10. The process of  claim 7  wherein said image acquiring is conducted by:
 (I) illuminating the substrate at the maximum pixel population area with the at least one illumination source; and 
 (II) capturing an image of the substrate at the maximum pixel population area with the digital camera. 
 
     
     
       11. The process of  claim 7  further comprising a linear drive for moving the illumination source and digital camera together across the substrate. 
     
     
       12. The process of  claim 11  wherein the planar substrate is moving and the linear drive moves perpendicular to the direction of travel of the substrate. 
     
     
       13. The process of  claim 11  wherein the planar substrate is stationary and the linear drive moves in two orthogonal directions relative to a surface of the planar substrate. 
     
     
       14. The process of  claim 1  wherein said adjusting step is conducted by adjusting an ink control mechanism to increase or decrease the amount of ink printed onto the substrate in one or more ink zones. 
     
     
       15. The process of  claim 1  further comprising presenting a visual representation of the one or more colored image portions, the maximum pixel population area, the actual, target and pure color values, a comparison of the color values, or combinations thereof, on a display screen. 
     
     
       16. The process of  claim 1  further comprising selecting a locator mark from one of said ink zones on said substrate, determining position coordinates for the locator mark in said pixellated digital representation, comparing the coordinates of the locator mark to the position coordinates of the one or more of said maximum pixel population areas, and directing the imaging assembly to said one or more of said maximum pixel population areas relative to the locator mark position coordinates. 
     
     
       17. A process for measuring and controlling a color value of one or more colored image portions which are printed on a planar substrate in a plurality of ink zones that extend across a width of the substrate, each colored image portion comprising one or more colors, wherein each color has a pure color value, the process comprising:
 (a) providing one or more colored image portions which are printed on a planar substrate with a quantity of ink in a plurality of ink zones that extend across a width of the substrate, each colored image portion comprising one or more colors, wherein each color has a pure color value; 
 (b) providing a memory which contains pure color value information in digital form for each color; 
 (c) providing a pixellated digital representation of said one or more colored image portions, said pixellated digital representation being divided into a plurality of digital paths corresponding to each of said ink zones, each digital path comprising a plurality of digital zones, and said pixellated digital representation being further divided into one or more color layers, each color layer corresponding to one of said one or more colors, and wherein said pixellated digital representation comprises target color values that correspond to the quantity of ink required to reproduce the one or more colored image portions for each color within each ink zone on the substrate; 
 (d) analyzing each of the color layers within each of the digital paths to determine a maximum pixel population area for each color within each of said digital paths, the maximum pixel population area having position coordinates and comprising a location within the colored image portion within the digital zone of a digital path having the target color value that is the closest target color value to the pure color value for its corresponding color within its digital path, and storing the maximum pixel population area position coordinates and its color value in the memory; 
 (e) modifying the one or more colored image portions printed on the planar substrate by increasing or decreasing the quantity of ink in one or more of said ink zones, said modified one or more colored image portions having modified target color values; 
 (f) scanning the substrate with a scanner at each maximum pixel population area location and determining modified target color values for each of said maximum pixel population areas, and storing said modified target color values for each maximum pixel population area in the memory; 
 (g) comparing and determining any difference between the modified target color values of each maximum pixel population area and the corresponding pure color value for each color, and storing said difference in the memory; 
 (h) providing at least one imaging assembly, wherein the imaging assembly is capable of capturing digital representations of said one or more colored image portions; 
 (i) controlling the positioning and linear movement of said imaging assembly across the planar substrate; 
 (j) selecting and acquiring one or more digital images with the imaging assembly of said one or more colored image portions on the substrate at the maximum pixel population area location for at least one of said colors in at least one of said ink zones, thereby producing the digital image of the maximum pixel population area; said digital image of the maximum pixel population area having an actual color value for said at least one color in said at least one of said ink zones; 
 (k) analyzing the digital image of the maximum pixel population area and measuring the actual color value for said at least one color; 
 (l) comparing and determining any difference between the actual color value and the pure color value, and storing said difference in the memory; and 
 (m) optionally adjusting the ink quantity on the substrate in the corresponding ink zone such that the difference between the actual color value and the pure color value is equivalent to the difference between said modified target color value and said pure color value determined in (g). 
 
     
     
       18. The process of  claim 17  wherein the option of adjusting the ink quantiy on the sustrate in step (M) is performed. 
     
     
       19. The process of  claim 17  further comprising repeating steps (i) through (m) to maintain color on the substrate such that the difference between the actual color value and the pure color value is equivalent to the difference between said target color value and said pure color value determined in (g) for each ink zone. 
     
     
       20. The process of  claim 17  wherein scanning step (f) is conducted with the imaging assembly of (h). 
     
     
       21. A process for controlling an amount of ink fed from a plurality of inking units in a multicolored printing press onto a planar substrate fed through the press, which substrate is in a web or sheet form, said substrate having one or more colored image portions printed thereon from the inking units, which image portions are printed across a width of the substrate in a plurality of ink zones, each colored image portion comprising one or more colors, wherein each color has a pure color value, the system being capable of functioning in the presence of or absence of a color bar, the process comprising:
 (a) providing one or more colored image portions which are printed on a planar substrate with a quantity of ink in a plurality of ink zones that extend across a width of the substrate, each colored image portion comprising one or more colors, wherein each color has a pure color value; 
 (b) providing a memory which contains pure color value information in digital form for each color; 
 (c) providing a pixellated digital representation of said one or more colored image portions, said pixellated digital representation being divided into a plurality of digital paths corresponding to each of said ink zones, each digital path comprising a plurality of digital zones, and said pixellated digital representation being further divided into one or more color layers, each color layer corresponding to one of said one or more colors, and wherein said pixellated digital representation comprises target color values that correspond to the quantity of ink required to reproduce the one or more colored image portions for each color within each ink zone on the substrate; 
 (d) determining whether a color bar is present, which color bar comprises a plurality of color patches, wherein at least one color patch is printed in each ink zone, wherein each color patch comprises one or more color layers; and 
 (e) if a color bar is not present, conducting step (I), and if a color bar is present conducting either step (I) or step (II):
 (I) (f) analyzing each of the color layers within each of the digital paths to determine a maximum pixel population area for each color within each of said digital paths, the maximum pixel population area having position coordinates and comprising a location within the colored image portion within the digital zone of a digital path having the target color value that is the closest target color value to the pure color value for its corresponding color within its digital path, and storing the maximum pixel population area position coordinates and its color value in the memory; 
 (g) comparing and determining any difference between the target color value of said maximum pixel population area and the corresponding pure color value for each color, and storing said difference in the memory; 
 (h) providing at least one imaging assembly, wherein the imaging assembly is capable of capturing digital representations of said one or more colored image portions; 
 (i) controlling the positioning and linear movement of said imaging assembly across the planar substrate; 
 (j) selecting and acquiring one or more digital images with the imaging assembly of said one or more colored image portions on the substrate at the maximum pixel population area location for at least one of said colors in at least one of said ink zones, thereby producing the digital image of the maximum pixel population area; said digital image of the maximum pixel population area having an actual color value for said at least one color in said at least one of said ink zones; 
 (k) analyzing the digital image of the maximum pixel population area and measuring the actual color value for said at least one color; 
 (l) comparing and determining any difference between the actual color value and the pure color value, and storing said difference in the memory; and 
 (m) optionally adjusting the ink quantity on the substrate in the corresponding ink zone such that the difference between the actual color value and the pure color value is equivalent to the difference between said target color value and said pure color value determined in (g); 
 (II) (n) providing at least one imaging assembly, wherein the imaging assembly is capable of capturing digital representations of said one or more colored image portions; 
 (o) controlling the positioning and linear movement of said imaging assembly across the planar substrate; 
 (p) selecting and acquiring one or more digital images with the imaging assembly of one or more of said color patches, thereby producing a digita image of the one or more color patches; said digital image of the one or more color patches having an actual color value for each of its one or more color layers; 
 (q) analyzing the digital image of the one or more color patches and measuring the actual color value for said one or more color layers; 
 (r) comparing and determining any difference between the actual color value and the pure color value, and storing said difference in the memory; and 
 (s) optionally adjusting the ink quantity on the substrate in the corresponding ink zone such that there is no difference between the actual color value and the pure color value. 
 
 
     
     
       22. The process of  claim 21  further comprising selecting a locator mark from one of said ink zones on said substrate, determining position coordinates for the locator mark in said pixellated digital representation, comparing the position coordinates of the locator mark to the position coordinates of the one or more of said maximum pixel population areas, and directing the imaging assembly to said one or more of said maximum pixel population areas relative to the locator mark position coordinates. 
     
     
       23. The process of  claim 21  wherein a color bar is present and further comprising selecting at least one locator mark from at least one of said ink zones on said substrate, wherein said at least one locator mark comprises a patch of the color bar, determining position coordinates for the at least one locator mark in said pixellated digital representation, determining position coordinates for each ink zone, comparing the position coordinates of the at least one locator mark to the position coordinates of either said maximum pixel population areas if (I) or to the position coordinates of at least one ink zone if (II), and directing the imaging assembly to said one or more of said maximum pixel population areas or said at least one ink zone relative to the locator mark position coordinates. 
     
     
       24. The process of  claim 21  wherein said imaging assembly comprises a digital camera and at least one illumination source. 
     
     
       25. The process of  claim 21  further comprising adjusting the ink quantity on the substrate in the corresponding ink zone such that there is no difference between the actual color value and the pure color value. 
     
     
       26. The process of  claim 21  further comprising repeating steps (i) through (m) to maintain color on the substrate such that the difference between the actual color value and the pure color value is equivalent to the difference between said target color value and said pure color value determined in (g) for each ink zone; or repeating steps (o) through (s), such that there is no difference between the actual color value and the pure color value for each ink zone. 
     
     
       27. A color control system for measuring and controlling a color value of one or more colored image portions which are printed on a planar substrate in a plurality of ink zones that extend across a width of the substrate, each colored image portion comprising one or more colors, wherein each color has a pure color value, the system comprising:
 (a) one or more colored image portions which are printed on a planar substrate with a quantity of ink in a plurality of ink zones that extend across a width of the substrate, each colored image portion comprising one or more colors, wherein each color has a pure color value; 
 (b) a memory for storing pure color value information in digital form for each color, and for storing a pixellated digital representation of said one or more colored image portions, said pixellated digital representation being divided into a plurality of digital paths corresponding to each of said ink zones, each digital path comprising a plurality of digital zones, and said pixellated digital representation being further divided into one or more color layers, each color layer corresponding to one of said one or more colors, and wherein said pixellated digital representation comprises target color values that correspond to the quantity of ink required to reproduce the one or more colored image portions for each color within each ink zone on the substrate; 
 (c) a first analyzer for analyzing each of the color layers within each of the digital paths to determine a maximum pixel population area for each color within each of said digital paths, the maximum pixel population area having position coordinates and comprising a location within the colored image portion within a the digital zone of a digital path having the target color value that is the closest target color value to the pure color value for its corresponding color within its digital path, which maximum pixel population area position coordinates and its color value are stored in the memory; 
 (d) a first comparator for comparing and determining any difference between the target color value of said maximum pixel population area and the corresponding pure color value for each color, which difference is stored in the memory; 
 (e) at least one imaging assembly, wherein the imaging assembly is capable of capturing digital representations of said one or more colored image portions; 
 (f) a controller for controlling the positioning and linear movement of said imaging assembly across the planar substrate; 
 (g) a selector for selecting and acquiring one or more digital images with the imaging assembly of said one or more colored image portions on the substrate at the maximum pixel population area location for at least one of said colors in at least one of said ink zones, thereby producing the digital image of the maximum pixel population area; said digital image of the maximum pixel population area having an actual color value for said at least one color in said at least one of said ink zones; 
 (h) a second analyzer for analyzing the digital image of the maximum pixel population area and measuring the actual color value for said at least one color; 
 (i) a second comparator for comparing and determining any difference between the actual color value and the pure color value, which difference is stored in the memory; and 
 (j) an adjuster for optionally adjusting the ink quantity on the substrate in the corresponding ink zone such that the difference between the actual color value and the pure color value is equivalent to the difference between said target color value and said pure color value.